Treating skins, hides, and pelts



Patented Feb. 14, 1939 TREATING SKINS, HID'ES, AND PELTS Edwin E. Ochs, Riverton, N. J., assignor. to Ruby Kid 60., Camden, N. J., a corporation of New Jersey No Drawing. Application January 27, 193'i, Serial N0. 122,662

4 Claims. (01. 195-6) This invention relates to an improvement in sidered desirable and even necessary to remove the processing of skins, hides and pelts (hereinfrom the skins prior to tanning, and prior to the after referred to collectively as skins) in prepadrenching and pickling operations which may ration for tanning, and the invention; has for its immediately precede tanning, all, or as much as 5 principal object the provision of means, applicapossible, of the residual calcium from the skins, ble to any or all of the preparatory processes and it is customary to employ extensive opera prior to pickling, drenching and tanning, where tions for the removal or neutralization of that lime or any calcium compound is or may have element. In those operations, also, it has been been used, for more adequately controlling that customary to employ acids some of which conelement of the processing medii. stitute a potential source of damage to the skins, m

Another object is to provide means whereby and requiring, therefore, exact and careful conskins, after lime treatment and resulting swelling, trol. In other instances, ammonium salts are may be brought back to the desired fallen or used but in every case the processes are calcubated cdndition, i. e., to a flaccid and approxilated to remove, and are of such a nature as necesmately neutral pH state, without removal of the sarily to e o e, t e Ca e greater p 15 lime content. tion thereof from the skins. These prior de- A more specific object of the invention is to liming operations, furthermore, both in their own provide a method of control of the aforesaid charnature and because of the limitations imposed acter, whereby the residual calcium content of the by the other essential preparatory processes, have skins at the termination of said preparatory never been capable readily of the control required 20 treatments shall be present wholly, or substanfor exactly uniform results. tially so, in the form of a neutral compound, or I have found that the presence of calcium, as compounds, of that element. such, in the skins in reasonable amounts is not Another object is to provide a method of condetrimental to the tanning process, and in fact is trol, as set forth, which shall, with safety, permit frequ nt y beneficiaI y facilitating the p 25 the presence in the skins at the termination of tion of skins by t active tanning agents, but said preparatory treatments of larger quantities that it is essential that the-calcium contained in of calcium than has been practical under the prior the skin shall be present in the form of a neutral practices, compound or compounds ofthat element. I have Still another object is to provide a method of discovered, f rther. that Carbon de (CO2) 30 the character described that shall be capable of constitutes an agent highly adapted for that p functioning efficiently with any character of pose, and one that is capable, as hereinafter deliquid or semi-liquid treating medium and indescribed, of affording the closely controlled and pendently and irrespective of temperature condihig y uniform results required the D 85 tions d pH v l tion of a consistently superior leather product.

Another and more general object is to provide In the practice of my invention, carbon dioxide a novel method of treatment in preparation for y be injected, a c to the liquid treatin tanning that shall yield a better conditioned and medium and in the presence of the skins in any superior skin and a correspondingly improved end or all of the conventional p epara y processes,

40 product. such, for example, as depilation, deliming, bating, 0

The invention further contemplates the proredu d falling. or in y o b nation or vision of a generally improved and advantageous j int w k of these processes. where, of course, method for bringing swollen skins to the proper lime or any calcium compound, is or has been pH value of the fallen or flaccid state. used. The quantity of CO2 thus injected is not Th s of lime in the processing of skins precritical and may be considerably in excess of the 45 paratory to tanning, in depilation for example, minimum required to convert the calcium content creates certain problems of a more or less comof the skins to the desired neutral form or conplex nature affecting the process as a whole. It dition. The minimum amount of CO2 required to becomes necessary, for example, in all subsequent produce the desired result may readily be detertreatments of the skins to take into account and mined by te and Since this agent s a Weak acid 50 to adequately provide for the presence in the in reaction, and cannot, therefore, adversely affect skin of that substance, the effect of the lime or the skin, there need be no critical consideration other calcium compound upon the treating meas to maximum amount, and an excess of even dium and its pH value, and primarily the effect considerable proportion is not detrimental.

upon the skin itself. In general, it has been con- When so used, the CO2 forms H2C'O3 with the water present, which readily penetrates the skins, and has the effect of converting the lime or other calcium content of the skin to the form of a neutral compound or compounds, and tends, further, to precipitate any soluble calcium present in the skin, also in the form of a neutral compound, and to thereby increase the calcium content of the skin. Since excess of CO2 may be employed without detrimental effect, positive assurance may be had that all, or substantially all, of the calcium present in the skins at the termination of the preparatory treatments shall be in the desired neutral form.

The use of carbon dioxide in accordance with my invention in no way complicates or requires modification of the conventional processes employed in the treatment of skins preparatory to tanning. The use of carbon dioxide on the other hand ends to simplify the conventional operations and to render them less critical in character. It is possible, for example, in the bating or other process to reduce the amount of or even to entirely eliminate the use of ammonium chloride or other buffer or d-eliming material required in the conventional procedures to maintain the pH value at a substantial constant.

The use of carbon dioxide in accordance with my invention has the additional advantage that it can be successfully employed in substantially any character of treating medium. It is to be noted further that by the use of this highly efficient medium for the stated purpose and the assurance that it afiords the elimination in the skins of calcium, except in neutral form, there is not the same necessity, as in the prior processes, for removing residual lime from the skins, and that accordingly the steps of the said prior processes calculated to effect a substantial removal of the calcium from the skins may be modified or eliminated, with the result that the amount of calcium present in the skin at the termination of the preparatory processes, all in the form of neutral compounds, may materially exceed the lime content of the skins under the prior proc- -1, esses, thereby facilitating and improving the subsequent tanning process as set forth above. It may be used, for example, in both sterile and non-sterile liquids, or in any combination of such liquids. It may be used also in the presence of liquids containing fermenting or fermentable substances, bacteria, molds, enzymes, catalysts or any of the chemicals or combinations of chemicals employed in the treatment of skins.

Instead of introducing carbon dioxide, as such, into the treating liquors, this agent may be gen erated or formed by reaction of suitable chemicals added to the liquid, or a combination of these two methods may be employed. The invention is not limited to any specific method or methods for rendering the carbon dioxide or carbonic acid available in the process for reaction With the calcium.

The invention may be further practiced by subjecting moist or wet skins to the action of a carbon dioxide atmosphere.

While the invention has application of particular value, as described above, in conjunction with treatments of skins by a calcium process,

it will be apparent that the use of carbon dioxide ii or carbonic acid in the manner set forth affords a highly useful method for neutralizing other alkalies, such for example as caustic soda, and the efiects of such alkalies upon the skins. In such cases, it has been found that the presence of the carbonic acid or carbonic acid gas afiords a sufficient buffer effect to bring the skins rapidly and economically to the proper pH value of the fallen or flaccid state.

I claim: i

1. In the preparation of skins for tanning, the process which comprises treating the skins with lime, and subsequently hating the calcium-swollen skins with prepared enzymes in the presence of carbon dioxide.

2. The process for bating lime-treated skins, which consists in subjecting the skins to the action of a prepared enzyme in the presence of carbon dioxide.

3. The process which consists in immersing lime-treated skins in a bath containing a solution of a prepared enzymic bating material, and regulating the pH value of said bath by injection of carbon dioxide.

4. The process which consists in bating limetreated skins with a prepared enzymic bating material, and regulating the pH value of the bating liquor by means of carbon dioxide.

EDWIN E. OCI-IS. 

